• Journal of Microbiology and Biotechnology
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• 제15권1호
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• pp.40-47
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• 2005

Modeling and simulation for simultaneous saccharification and fermentation (SSF) process in bioconversion of paper mill sludge to lactic acid was carried out. The SSF process combined the enzymatic hydrolysis of paper mill sludge into glucose and the fermentation of glucose into lactic acid in one reactor. A mathematical modeling for cellulose hydrolysis was developed, based on the proposed mechanism of cellulase adsorption deactivation. Another model for simple lactic acid fermentation was also made. A whole mathematical model for SSF was developed by combining the above two models for cellulose hydrolysis and lactic acid fermentation. The characteristics of the SSF process were investigated using the mathematical model.

• KSBB Journal
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• 제28권6호
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• pp.366-371
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• 2013

Ethanol productions were performed by separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) processes using seaweed, Enteromorpha intestinalis (sea lettuce). Pretreatment conditions were optimized by the performing thermal acid hydrolysis and enzymatic hydrolysis for the increase of ethanol yield. The pretreatment by thermal acid hydrolysis was carried out with different sulfuric acid concentrations in the range of 25 mM to 75 mM $H_2SO_4$, pretreatment time from 30 to 90 minutes and solid contents of seaweed powder in the range of 10~16% (w/v). Optimal pretreatment conditions were determined as 75 mM $H_2SO_4$ and 13% (w/v) slurry at $121^{\circ}C$ for 60 min. For the further saccharification, enzymatic hydrolysis was performed by the addition of commercial enzymes, Celluclast 1.5 L and Viscozyme L, after the neutralization. A maximum reducing sugar concentration of 40.4 g/L was obtained with 73% of theoretical yield from total carbohydrate. The ethanol concentration of 8.6 g/L of SHF process and 7.6 g/L of SSF process were obtained by the yeast, Saccharomyces cerevisiae KCTC 1126, with the inoculation cell density of 0.2 g dcw/L.

• KSBB Journal
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• 제30권3호
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• pp.125-131
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• 2015

Kluyveromyces marxianus is a well-known thermotolerant yeast. Although Saccharomyces cerevisiae is the most commonly used yeast species for ethanol production, the thermotolerant K. marxianus is more suitable for simultaneous saccharification and fermentation (SSF) processes. This is because enzymatic saccharification usually requires a higher temperature than that needed for the optimum growth of S. cerevisiae. In this study, we compared the fermentation patterns of S. cerevisiae and K. marxianus under various temperatures of fermentation. The results show that at a fermentation temperature of $45^{\circ}C$, K. marxianus exhibited more than two fold higher growth rate and ethanol production rate in comparison to S. cerevisiae. For SSF using starch or corn stover as the sole carbon source by K. marxianus, the high temperature ($45^{\circ}C$) fermentations showed higher enzymatic activities and ethanol production compared to SSF at $30^{\circ}C$. These results demonstrate the potential of the thermotolerant yeast K. marxianus for SSF in the industrial production of biofuels.

• 대한환경공학회지
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• 제32권6호
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• pp.609-614
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• 2010

유기성 폐기물인 음식물쓰레기를 이용하여 유용한 에너지원인 바이오에탄올을 생산하고자 하였으며, 에탄올 생산 균주는 Saccharomyces cerevisiae를 이용하였다. 음식물쓰레기의 당화를 위하여 carbohydrase와 glucoamylase 효소를 이용한 결과 carbohydrase가 glucoamylase보다 당화효율이 우수하였으며, carbohydrase 이용시 건조 음식물쓰레기 기준 glucose 생산량 0.63 g/g-TS을 얻을 수 있었다. 에탄올 생산은 동시당화발효에서 0.44 g/$L{\cdot}hr$, 분리당화발효가 0.27 g/$L{\cdot}hr$이었다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제3권2호
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• pp.55-60
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• 1998

Various Saccharomyces cerevisiae strains were transformed with a 2 ${\mu}$-based multicopy expression plasmid, pYIGP, carrying Kluyveromyces marxianus inulinase gene under the control of GAPDH promoter. Among then two strains, SEY2102 and 2805, showed high levels of cell growth and inulinase expression, and were selected to study their fermentation properties on inulin. Jerusalem artichoke inulin was more effective for cell growth (10∼11 g-dry wt./L at 48 hr) and inulinase expression (1.0 units/mL with SEY2102/pYIGP and 2.5 units/mL with 2805/pYIGP) than other inulin sources such as dahlia and chicory. It was also found that maximal ethanol production of 9 g/L was obtained from Jerusalem artichoke inulin at the early stationary phase (around 30 hr), indicating that recombinant S. cerevisiae cells secreting exoinulinase could be used for the simultaneous saccharification of inulin and ethanol fermentation.

• KSBB Journal
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• 제13권1호
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• pp.38-43
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• 1998

Application of pervaporative extraction of ethanol to simultaneous saccharification and fermentation(SSF) of cellulose was investigated. From batch experiments, optimum cellulose substrate and enzyme loadings were found to be 10% and 15 IFPU/g cellulose, respectively. The cellulose conversion was lowered in fed-batch system due to the ethanol accumulation. The activity of the yeast Saccharomyces uvarum used in this study was significantly reduced at ethanol concentrations above around 40 g/L. From pervaporation experiments using PDMS membrane, ethanol was efficiently separated at 38$^\circ C$ and 10 mmHg of a down stream pressure. The pervaporation unit with 240 cm$^2$ of surface area was combined into the SSF reactor. The continuous removal of ethanol by pervaporation during SSF resulted in an improved cellulose conversion. Within the scope of this experiment, ethanol yields in the pervaporative SSF and simple SSF were 68.3% and 56.6%, respectively. The permeate flux for SSF broth pervaporation was about one-half that for the pervaporation of aqueous ethanol solution. Accordingly, the development of a membrane with higher ethanol selectivity and flux will increase the feasibility of this technology.

• KSBB Journal
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• 제5권4호
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• pp.329-334
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• 1990

In an attempt to develop a novel process for ethanol production from starch, a simultaneous saccharification and fermentation (SSF) process using Zymomonas mobilis and amyloglucosidase (AMG) was studied in continuous modes. Compared with a conventional cylindrical column type of fermentor, the tapered column type of fermentor was found to be superior in terms of reactor performance for ethanol fermentation. The tapered columm fermentor packed with coimmobilized Z. mobilis and AMG alleviated the problems which were associated with CO2 evolution and provided a significantly better flow pattern for both liquid and gas phases in the fermentor without channelling. However, the fluidized bed type of tapered column fermentor using flocculent strain of Z. mobiles and immobilized AMG showed lower productivity (5.2g/1/h) than that of packed bed type of tapered column fermentor(9.2g/l/h).

• KSBB Journal
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• 제15권5호
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• pp.458-463
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• 2000

Production of acetic acid from cellulosic biomass by Simultaneous Saccharification and Extractive Fermentation (SSEF) was investigated. The homoacetate organism used in this study was a strain of Clostridium thermoaceticum, ATCC # 49707. A batch operation of Simultaneous Saccharification and Fermentation(SSF) using ${\alpha}$-cellulose at pH 5.5 and 55$^{\circ}C$ yielded 40% conversion of cellulose to acetic acid, while a fed-batch SSF operation produced a maximum acetic acid concentration of 25 g/L, with 50% overall yield. In-situ extractive fermentation to reduce the end-product inhibition on both bacteria and enzyme was carried out. in a batch SSEF using 200 g/L IRA-400 resin, acetic acid concentration reached to 23.9 g/L and acetic acid yield and productivity were observed to be 48% and 0.20 g/L-hr, respectively.

• 한국식품과학회지
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• 제23권6호
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• pp.739-744
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• 1991

호화시킨 쌀을 액 당화한 후 젖산발효하고 균질화하여 호상 쌀젖산발효물을 제조하였다. 발효시 ${\alpha}$-아밀라제와 글루코아밀라제를 각각 0.02%수준으로 처리하여 2차 당화와 동시에 발효를 진행함으로써 쌀젖산발효물의 품질을 크게 향상시킬 수 있었다. 이들 효소처리에 의하여 쌀젖산발효물의 신맛과 단맛이 증대되었으며 꺼끌꺼끌한 촉감을 주는 불용성 고형물 입자의 크기가 감소하였다. 쌀젖산 발효물의 관능적 품질은 매우 양호하였으며 기호도가 높았다. 최적화된 공정에 의거하여 제조된 쌀젖산발효물의 이화학적 특성을 조사하였다.

• Journal of Microbiology and Biotechnology
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• 제27권9호
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• pp.1649-1656
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• 2017

In simultaneous saccharification and fermentation (SSF) for production of cellulosic biofuels, engineered Saccharomyces cerevisiae capable of fermenting cellobiose has provided several benefits, such as lower enzyme costs and faster fermentation rate compared with wild-type S. cerevisiae fermenting glucose. In this study, the effects of an alternative intracellular cellobiose utilization pathway-a phosphorolytic pathway based on a mutant cellodextrin transporter (CDT-1 (F213L)) and cellobiose phosphorylase (SdCBP)-was investigated by comparing with a hydrolytic pathway based on the same transporter and an intracellular ${\beta}$-glucosidase (GH1-1) for their SSF performances under various conditions. Whereas the phosphorolytic and hydrolytic cellobiose-fermenting S. cerevisiae strains performed similarly under the anoxic SSF conditions, the hydrolytic S. cerevisiae performed slightly better than the phosphorolytic S. cerevisiae under the microaerobic SSF conditions. Nonetheless, the phosphorolytic S. cerevisiae expressing the mutant CDT-1 showed better ethanol production than the glucose-fermenting S. cerevisiae with an extracellular ${\beta}$-glucosidase, regardless of SSF conditions. These results clearly prove that introduction of the intracellular cellobiose metabolic pathway into yeast can be effective on cellulosic ethanol production in SSF. They also demonstrate that enhancement of cellobiose transport activity in engineered yeast is the most important factor affecting the efficiency of SSF of cellulose.